Conversation timing in telephone systems



y 8, 1953 c. LOMAX 2,647,163

CONVERSATION TIMING IN TELEPHONE SYSTEMS Filed Jan. 5, 1950 I 5 Sheets-She et 1 l3! g) FINDER SWITCH INVENTOR. CLARENCE E. LOMAX FIG. {M4

ATTORNEY y 8, 1953 c. E. LOMAX 2;647,163

CONVERSATION TIMING IN TELEPHONESYSTEMS Filed Jan. 5, 1950 5 Sheets-Sheet 2 20' OPER. POS.

SELECTOR C207 I I S TC POSITION E .fb

CONNECTOR CIRCUIT CONNECTOR SWITCH I I I 265 LINE 275 0234 I }CIRCUIT I 25% 263 I [C232 /-C23| I 272 262 240 0232 I 27| l C23I L Irj 26l |To LINE CIRCUIT 24] I FINDERS "'7 244, I

INVENTOR. CLARENCE E. LOMAX ATTORNEY July 28, 1953 c. E. LOMAX 6 CONVERSATION TI'MING'iN TELEPHONE1XSTEM Filed Jan. 5, 1950 5Z h t$heet 3 TO OTHER LINE CIRCUIT IN LINE CIRCUIT LINE CIRCUIT FROM CONN.

N DIST. a DISTRIBUTOR a 0318 o COMMON COMMON EQUIPMENT EQUIPMENT INVENTOR. CLARENCE E. LOMAX ATTORNEY July 28, 1953 c; E. LOMAX v 2,647,163

CONVERSATION TIMVING' iNTELE-FHONE -S2Sihlg5; I Filed Jan. 5, 1950 43| 43o FINDER SWITCH 'LINK so- 440 H I l "fi INVENTOR. FIG 4 CLARENCE E. LOMAX July 28, 1953 c. E. LOMAX 2,647,163

CONVERSATION TIMING IN TELEPHONE SYSTEMS Filed Jan. 5, 195 0 5 -Sh eets--She.et.5 FINDER SWITCH RA562 RA552 RA559 RA542 RA553 l RA555 INVENTOR. F l G. 5 CLARENCE E. LOMAX ATTORNEY Patented July 28, 1953 CONVERSATION TIMING IN TELEPHONE SYSTEMS Clarence E. Lomax, Chicago, Ill., assignor to Automatic Electric Laboratories, Inc., Chicago, III., a corporation of Delaware Application January 5, 1950, Serial No. 136,922

14 Claims.

This invention relates in general to telephone systems and more particularly to telephone systems which utilize conversation timing of established telephone connections, the connection being automatically disconnected a certain interval of time after it was first established.

The number of switches required in an automatic telephone exchange to give proper service is determined by the number of calls made during the busy hour or hours and the length of time the connection is held during this period. The generally accepted formula is that one eighth of the total twenty-four hour daily load is carried during the one busiest hour of the day. If the length of time of the calls during the busy periods could be shortened, a greater number of calls could be completed over the same number of switches and also certain subscribers would be induced to make their calls during non-busy hours so as to have unlimited conversation time, the combined result being a substantial reduction in the number of switches over the number required to give proper service when no periodic conversation timing is employed. It should be realized that it would not be advisable to subject certain calls, such as calls from business establishments, to conversation timing at any time of the day and the same applies to toll calls made from any subscriber including those subscribers normally afiected by conversation timing. It would also be advisable to allow for a disabling of the conversation timing apparatus during the peak load periods should it be warranted by a light trafiic load during the normally busy period. It is with these foregoing facts in mind that this invention was conceived.

One object of this invention is to provide conversation timing with automatic disconnect, con trolled in line finders or the primary trunks of automatic switch trains, of telephone connections established by certain subscribers having access to the lineiinders or primary trunks, while similar connections established by certain other subscribers with access to the same linefinders or primary trunks are not subject to the conversation timing.

Another object or the invention is to provide that the conversation timing is operative only during certain periods of the day, normally the periods when the switching system is carrying the heaviest daily load.

Another object of the inventionis to prevent conversation timing on the connections normally subject to it when the call is of a special class, such as a toll call, even during the peak load periods.

Another object of the invention is to provide an operator or other proper person with control of the conversation timing equipment to such an extent that they could disable the conversation timing equipment at any time during the peak load period in case a light traffic condition warranted no conversation timing during a normally busy period.

One feature of this invention is the provision, in a linefinder, of a circuit designed to automatically interrupt the talking connection established through the linefinder a certain period of time after the connection was first established but only during certain periods of the day.

Another feature of this invention is the provision, in a 200 point linefinder, of a circuit designed to automatically interrupt the talking connection established through the linefinder a certain period of time after the connection was first established, the interrupting circuit being operative only on connections established from subscriber lines in one of the hundreds groups of lines having access to the linefinder, the second hundred group of lines having an unlimited time to retain the connections established from them.

Another feature of this invention is the provision, in a step-by-step Strowger linefinder, of a circuit designed to automatically interrupt the talking connection established through the linefinder a certain period of time after the connection was first established, the interrupting circuit being operative only on connections established from subscribers lines on certain vertical levels of the contact banks of the switch, the subscribers lines on the other levels of the switch bank having an unlimited conversation time period.

Another feature of this invention is the provision, in a linefinder, of a circuit designed to automatically interrupt the talking connection established through the linefinder a certain period of time after the connection was first established, the interrupting circuit being operative on certain subscribers lines regardless of the hundreds group or bank level they are in, the application of the interrupting circuit being determined by the bank wiring of a fourth line bank contact provided with every subscriber line having access to the linefinder.

- Another feature of this invention is the provision, with the conversation timing circuit in the three methods above for discriminating between subscribers having access to the linefinder, of a timing device for rendering the conversation timing circuit operative only during certain periods of the day, for instance two hours in the morning and two hours in the evening.

Another feature of this invention is the provision of a key circuit at an operator's position or exchange attendants desk for disabling the conversation timing circuit during light traflic load periods.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawings, showing by way of example, a preferred embodiment of the inventive idea.

Figs. 1, 2, 3, 4 and 5 depict the telephone system which best illustrates the present invention, a system very similar to the telephone system shown in the Patent 2,214,908 of Lomax and Bakker, September 17, 1940, the two systems being identical except for the modifications incor-- porated to show the present invention. For simplicity the entire system shown in Patent 2,214,908 will not be again shown in detail and described but only those parts of the system which will help to disclose the present invention will be shown in detail. The designation numbering of the component parts of the system shown in this invention is made to correspond in the greatest degree possible to the designation numbering of the similar component parts of Patent 2,214,908 and a reference to the above-named patent will quickly disclose their inter-relationship with the parts of the system not shown in detail.

More particularly, Fig. 3 in part illustrates the subscriber line IOI, one of the lines in the first hundreds group of lines in a particular 200 line group; line circuit I00 associated with line IOI; subscriber line I06, one of the lines in the second hundreds group of lines; and line circuit I I0 associated with line I06.

Fig. 2 illustrates the selector switch 200, a part of the finder-selector link, including the switching mechanism 20I; the operators position 2I0; the connector switch 2I5, one of the first group of connectors accessible to the first group of links, and connector switching mechanism 225; the B subscribers line 230; line circuit 240 associated with line 230; timing device 250; and timing cam 243 and associated equipment.

Fig. 3 in part also illustrates the finder switch 3I0 and selector switch 3II which make up the link I0 of the system, link I0 being included in the second group of links which normally serve a second portion of the 200 lines; the distributor and common equipment 3I2 associated with the second group of links which normally assigns idle links in the second group to calling lines in the second portion but will, when all the links in the first group of links are busy, assign idle links in the second group of links to calling lines in a first portion of the 200 lines; and the distributor and common equipment 300 associated with the first group of links which normally assigns idle links in the first group of links to calling lines in a first portion of the 200 lines but which will, when all the links in the second group of links are busy, assign idle links in the first group of links to calling lines in the second Portion of the 200 lines. Fig. 3 is associated with the finders of Figs. 1, 4 and 5.

Fig. 1 illustrates a finder switch I similar to the finder switch I30 of the above-named patent with a few modifications, the finder switch being a part of the link 60 which is included in the first group of links and provided with the distributor and common equipment 300. This finder comprises a conversation timing feature which times and disconnects calls made from subscribers lines in the first hundreds group of subscriber lines 4 and is inoperative on calls from the second hundreds group of lines.

Fig. 4 illustrates a finder switch 430 similar to the finder I30 of Fig. 1 modified to provide discrimination as to conversation timing of calls on the basis of the contact bank level of the Strowger switch, shaft springs S413 being provided to accomplish this discrimination. This finder of Fig. 4 is substituted in link 60 for the finder of Fig. 1 to show the modification.

Fig. 5 illustrates a finder circuit 530 similar in most respects to the finders of Figs. 1 and 4 but modified to provide discrimination between individual subscriber lines rather than group discrimination by means of a fourth bank contact in each line bank contact set. This finder of 'Fig. 5 is substituted in link 60 for the finder of Fig. 1 to show a further modification.

Figs. 1, 2 and 3 in conjunction form one method for utilizing this invention. Figs. 4, 2 and 3 illustrate a second method and Figs. 5, 2 and 3 show a third method.

Referring now to Figs. 1, 2 and 3, when the subscriber at the calling substation A initiates a call over the line I M, the line circuit I00 operates to ground control conductor CI05 to mark line IOI as busy to the connector switches having access thereto, applies battery potential to the control conductor CI04 to mark the rotary positions of the contact sets in the contact banks of the Strowger mechanisms included in the finder switches terminating the line IN, and grounds control conductor CI to thereby cause ground potential to be applied by way of the circuit network I9I to the start conductor C3I6 extending to the distributor 300 and to also cause the ground potential to mark, by way of circuit network I9I and the contacts in the vertical banks in the Strowger mechanisms included in the finder switches, the levels wherein line IOI is terminated, the contact in the vertical bank in the Strowger mechanism I40 included in the finder switch I30 being indicated at I48.

The ground closed to the control conductor CI90 and by way of circuit network I9I to the start conductor C3I6 initiates operation of the distributor 300, thereby to cause the preselected idle one of the first group of links to be assigned to the use of the calling subscriber line IOI, in this case link 00. More particularly, distributor 300 operates to place ground potential on finder start conductor C3I8 and ground potential on vertical conductor C320. Ground potential on conductor C3I8 causes relay RI40 to operate. Relay RI40 on operating closes a path between line conductors CH6 and CH1 by way of contacts RAI II and resistance I2'I to seize the selector circuit 200, closes ground to the control conductor CI I8 by way of contacts RAMA, RCMB, R0024 and R0623, closes conductor CI38 to the distributor 300 by Way of the second test conductor 0326 at RAI IZ, prepares the circuit from the rotary magnet MI'II to the distributor 300 by Way of RAI4'I, RAI5'I, RAISE and rotary conductor C324, and closes the circuit from vertical conductor C320 to the finder vertical magnet MI'I0 through contacts RAMS. The ground closed to conductor CI I8 thru RAIM and RCMG energizes the lower winding of the electro-polar relay R600 but this electro-polar relay is so designed that it will not operate on its lower Winding alone and so remains unoperated at this time. The ground potential on the vertical conductor C320 causes the vertical magnet MI'I0 to operate to step the Strowger switch mechanism I40 one step in the vertical'direction and to connect, at MAi'I0, ground to interrupter conductor C3I9. The ground connected to interrupter conductor C3I9 causes the distributor 300 to operate to remove the ground from vertical conductor C320 to cause the vertical magnet MI'I0 to restore, thereby removing the ground at MAI 10 from conductor C3I9. The removal of ground from conductor C3I9 causes the distributor 300 I to operate to reconnect ground to conductor C320 to again cause the vertical magnet MIlii to operate to step the Strowger switch mechanism I40 an additional step in the vertical direction and to reconnect ground to conductor 03!?) by way of MAI "I0. The above cycle of operations is continued, the vertical magnet MII and the distributor 300 interacting, to step the switch mechanism I40 in a vertical direction until the vertical wiper I41 engages the contact in the vertical bank associated therewith having marking ground potential thereon. In the present instance, the vertical wiper I 4? is driven vertically two steps at which time it engages contact I48 having the marking ground potential thereon. This ground on conductor CI03 from the line circuit I00 is closed thru contact I43 and wiper M7 to the distributor 300 by way of first test conductor C3I I. This ground on first test conductor C3I'I causes the distributor 300 to operate to remove the ground from vertical conductor C320 so that the vertical magnet M I10 will restore and also to connect ground on rotary conductor C324.

It is noted that when the switch mechanism I40 of the finder I is operated away from its normal position by the first operation of the vertical magnet Mlm, the sets of ofi-normal switch springs SHE and SI'I0 are actuated. More specifically, the switch spring I8I disengages from spring I82 and engages spring I80 and spring I18 disengages from spring I11 and engages spring I36. Their functions will become apparent hereinafter.

This ground on rotary conductor C324 from the distributor 300 is closed to the rotary magnet MI'II by Way of RAI65, RAEW and RAI47. When energized over the above traced circuit, the rotary magnet MI'II operates to step the Strowger switch mechanism I 30 of the finder switch I30 one step in the rotary direction and to connect, at MAI'H, ground to interrupter conductor C3I9. This ground on conductor C3I9 causes the distributor 300 to operate to disconnect the ground from rotary conductor C324 to thereby cause the rotary magnet MI II to restore. Upon restoring, magnet MIH removes ground, at MAI'H, from interrupter conductor C3I0 to cause the distributor 300 to operate to re-connect ground to rotary conductor C324 and thus reenergize the winding of the rotary magnet Mi 7 I. ihe rotary magnet MIII operates to cause the switch mechanism I40 to take an additional step in the rotary direction and to re-conneot ground to interrupter conductor C3I3. The rotary magnet MIiI and distributor 300 continue to interact in the manner described above until the switch mechanism I40 is rotated to the position of the contact set terminating the calling subscriber line IOI, at which time the wiper I43 of the upper wiper set engages the contact terminating the control conductor CI 04 of line IOI, assuming that the line IOI is accessible to the upper wiper set of the switch mechanism I40, whereupon a circuit is completed from the distributor 300 for seizing the calling subscriber line IOI by way 6 of control conductor CI04, wiper I43. and first test conductor C3I'I. The distributor 300 operates to open the circuit to the rotary magnet MIII over rotary conductor C324 to prevent further operation of the rotary magnet and closes ground to the conductor C323. Ground on the conductor C323 closes the circuit to switching relay RI00 by way of RAI55. Relay RI operates, opens a further point in the circuit to the rotary magnet MI'II at R-AI65, and closes a holding circuit to itself from ground by way of RAIN, RCI46 and RAI64. Upon operating, switching relay RIBO also connects a first set of conductors I3I terminated by the upper wiper set to the trunk line I I5 extending between the finder switch I30 and selector switch 200. Specifically, the conductors C533 and CI34 of the conductor set I3I are respectively connected at RAI62 and RAIB3 to the conductors CI I1 and CI I8, respectively, of the trunk line H5 and conductor CI32 of the conductor set I3I is connected thru the upper winding of electro-polarized relay R800 at RAIBI to the conductor CI I6 of the trunk line IE5. Ground potential standing on line conductor CI I7 and battery potential standing on line conductor CI I6 in the selector 200 at this time energize the upper winding of relay R000 but the electro-polar relay R600 is so designed that, with the circuit to the upper winding closed in such a manner as described, the field set up by the upper winding opposes the field set up by the lower winding and the relay R600 will not operate. Relay R600 will only operate when the battery potential is reversed on the line conductors CH1 and 0| I6 as will hereinafter be described.

Also, upon operating, relay RI60 opens a part of the incomplete circuit to the release magnet MI12 at RAISE and RCIBB and prepares a part I of the circuit to'supervisory lamp LI28 thru RAISE and RCIG'I, interrupts at RAI60 a point in the circuit for energizing relay RI50 from the distributor 300 over conductor C325 thereby to prevent operation of the switching relay RI50 at this time, and closes ground to the distributor 300 over guard conductor C322 thru switch springs I and NH, RAI69, and switch springs I84 and I85. This ground closed to the guard conductor C322 causes the release of the dis tributor 300 which then operates to locate the next idle link circuit available to the distributor in accordance with the pre-selecting feature of this linefinder system and also marks this link 60 busy to the distributor 300 during subsequent selecting operations of the distributor 300 while searching for idle links in the first group of links.

Upon this release of the distributor 300,-ground is removed from start conductor C3I8 in the distributor 300 and relay RI 40 restores, interrupts the first-mentioned path between line conductors CH6 and CI I! of trunk line H5 at RAI4I, closes an alternate path at RAI43 for applying the busy marking ground potential to guard conductor C322 from ground thru switch springs I80, IEH,

I85 and I84, interrupts points in the circuits to the vertical magnet MI'IG and rotary magnet MI'H at RAMS and RAM! respectively, and closes a circuit to the supervisory lamp LI28 at RAIM by way of RCI45, switch springs I86, I81, I10 and I76 and RAIES and RCIB'I. The lighted lamp LI28 indicates to the exchange attendant that the link is in use. Relay RI40 on restoring also removes ground at RCI4B from the conductor C I I8 and at this time relay RI60 is held operated and the upper winding of relay R600 7 held energized byground on the conductor C! !8 from the selector circuit 200, the selector circuit 200 in turn being held under control of the subscriber substation A over the line loop in a well known manner.

At this time, the distributor 300 is completely released and the selector 200 rendered operative in response to impulses from the calling subscrib er substation A to establish a connection to the called subscriber substation B.

The selector 200 responds to the first digit of the directory number of substation B dialed by the subscriber at substation A and operates in a well known manner to cause the Strowger mechanism to step to seize an idle connector in the first group of connectors accessible to the first group of links, assumed in this case to be connector 2 !5. Upon seizing the connector 2 !5, the selector 200 completes a line loop circuit between the subscriber substation A and the connector switch 2I5 in a well known manner. The conhector-switch 2!5 operates to apply ground potential to conductor C2! and through the selector 200 in turn to conductor C! !8 to hold relay RIB!) under the control of the connector 2 !5, the ground which had been connected to conductor C! !8 in the selector circuit 200 being removed at this time. Thus the selector 200 and line finder I30 are held under the control of the connector 2!5 in a well known manner.

The connector 2!5 responds to the final two digits in the called subscribers directory number and seizes the line circuit 240 of the called line 230, assuming the same to be idle. The called line is rung in the usual manner, ring-back tone being sent back to the calling party from the connector 2 I5.

When the subscriber at the substation Banswers, relay R220 in the connector switch 2!5 operates in a well known manner to reverse battery potential on the line conductors C2!2 and C2!3. More specifically, the ground potential through the upper winding of relay R220 which had been connected to the line conductor C2 !3 by way of RG28! and R0283 is now transferred to line conductor 02 !2 by way of RA285 and RC284 and the battery potential through the lower winding of relay R220 which had been connected to line conductor C2!2 by way of R0286 and R0284 is now transferred to line conductor C2 !3 by way of RA282 and R0283. This reversal of potential on the line conductors C2!2 and C2!3 causes a reversal in current flow through the upper winding of the electro-polar relay R600, the circuit being traced from ground thru the upper winding of relay R220, RA285, RC284, C212, wiper 202, CH6, RAIBI, the upper winding of relay R600, C!32, wiper !4!, CW3, the calling subscribers substation A, CI02, wiper I42, Cl33, RAI62, C! !1, wiper 203, C2I3, R0283, RA282, to battery potential thru the lower winding of relay R220. This reversal of current in the upper Y winding of electro-polar relay R600 causes the field set up thereby to aid the field set up by the lower winding and the electro-polar relay R600 operates. It should be noted that relay R600 is designed so as to be slow to operate so that it will not operate on momentary line disturbances. Upon operating, relay R600 shunts its upper winding by means of RA60 the energized lower winding being sufiicient to hold the relay R600 in its operated position once the relay has operated. Also, relay R600 closes a point in the circuit from timer conductor C! to the lower winding of relay R6l0 at RA602 for reasons to be hereinafter explained.

It is desired that the timing and automatic disconnect of established calls feature in this system be operative only during certain fixed periods of the day, normally the periods when the traflic through the system is heaviest. Therefore, referring to Fig. 2, there is provided a timing device comprising a cam 243 driven by a synchronous motor (not shown) which rotates continuously in a manner similar to the hour hand of a clock at the rate of one revolution every twenty-four hours. Notches 244 out in the cam 243 represent certain lengths of time in a day and are so positioned on the cam that they will cause the operation of the cam springs 24! during certain pre-selected periods of the day, normally those periods when the exchange traflic is at a peak. For instance, the cam 243 could be so arranged that notches 244 would cause cam springs 24! to close at 9 a. m. and remain closed until 10 a. m. or 10:30 a. m. and again close at 4 p. m. and remain closed until 6 p. m. every day of the week, these periods normally being among the heaviest trafiic periods of the day.

A second timing device 260 is provided which determines the length of time that a call subject to timing and automatic disconnection will be allowed. This timing device 260 consists of five cams 26! to 265 inclusive driven by a synchronous motor (not shown) at constant speed, each cam having an upraised portion thereon, these upraised portions being placed relative to each other so that they will operate their associated cam springs 21! to 215 inclusive consecutively at spaced periods ranging to 2 minutes each. This timing device 260, like the timing device 243, is in continuous operation.

If the call from the first group of lines is made during one of the aforementioned heavy load time periods, the operation of relay R600 closes a circuit from the timer conductor 25! to the lower winding of relay R6 0 by way of closed cam springs 24!, the normally closed key 242, RA602, and RA626. When this circuit is closed to the lower winding of relay R6l0, or soon thereafter, ground is closed to the timer conductor C25! by the closing of cam springs 21! by cam 26! and to the lower winding of relay R6l0 by way of cam springs 24!, key 242, RA602, and RA626. Relay R6l0 on operating closes a circuit to its upper winding by way of RA6l3, R0621, R0628, RC624 and RC623 to ground standing on conductor CH8 from the connector circuit 2!5 to hold itself operated when the ground is removed from conductor 25! by the restoration of cam springs 21!, opens a point in the circuit to the signal tone relay R630 at RAE! and closes the circuit from timer conductor 252 to the lower winding of relay R620 by way of RA6!2. Two minutes after timing device 260 closed the ground to timer conductor 25!, cam 262 causes ground to be closed to timer conductor 252 by way of cam springs 212 thus causing relay R620 to operate through its lower winding. On operating, relay R620 closes a circuit to its upper winding from ground on conductor CH8 through RA625 to hold itself operated after the ground is removed from timer conductor 252 by the restoration of cam springs 212, closes a part of the circuit to signal tone relay R630 at RA62!, transfers the holding circuit to the upper winding of relay R6|0 from conductor CH8 to timer conductor 253 by way of RC621 and RA629 and thus to ground through the closed cam springs 213,

amuse 9 transfers the holding circuit to relay RI66 from ground on conductor C'I I8 by way of R0624 and R0623 to ground on timer conductor 255 through closed cam springs 215 by way of RA622 and RC624, and opens the circuit from conductor I to the lower winding of relay Riilfl at RA626. Two minutes after cam springs 272 were operated to ground timer conductor 252, cam 263 causes ground to be removed from conductor 253 by opening cam springs 276 thus opening the circuit to the upper winding of relay R6I6. Relay R616 restores, closes the circuit from timer conductor 254 to signal tone relay R636 by way of RABH and. RAEiil, and opens a part of the circuit to the lower winding of relay R626 from timer conductor 252 at RA6l2. Approximately two m nutes after the ground had been removed from timer conductor 253, cam 264 causes ground to be closed to conductor 254 through cam springs 216 to relay R636 by way of RABII and RA62I.

Relay operates to place a tone over conductor C656 to the line conductors by way of RAEEI to inform the parties that they are about to be disconnected. A few seconds after relay R636 has operated to give this tone signal, cam 265 opens cam springs 275 to remove ground from conductor 255, thus opening the circuits thru RA622 and R0624 to the lower winding of relay R666 and to relay R566 by way of RAI64. Relay R666 restores. Relay RI 66 restores, closes a circuit to the release magnet MHZ by way of RAIM, RCMS, switch springs E86, N31, I18 and H6, RAI66, R0566 and RAMS, disconnects the conductors CV62, CI33 and C164 of conductor set I3? from conductors CI 56, CI IT and CI I8 respectively of trunk line I I5 at RAI6i, RAIGZand RAISE respectively, opens a multiple circuit to the guard conductor C622 at RAHSS, and opens the circuit at RCIS'I to extinguish the lamp Ll28.

The release magnet M572 operates to return the Strowger switch mechanism I66 of the finder switch 1'36 to its normal position. When the switch mechanism i 36 has reached the normal position, the vertical off-normal switches SI'I5 and SW9 return to normal. The circuit to the release magnet MHZ is opened at switch springs I 76 and ill; and the release magnet MHZ restores. The subscribers line circuit i 66 is re-' leased. The circuit to the guard conductor C322 is' transferred from ground at switch spring I86 to ground on conductor CI i 8 from the subsequent switch train, the latter circuit being traceable from ground on conductor Ci l8, switchsprings 82 and 965, RAI63, and switch springs I85 and M6 to conductor C322. The finder switch I'36is thus kept marked as busy to the distributor 366 until the subsequent switch train releases.

Opening the line conductors at RAISI and RAIEE by the restoration of relay Rl66 causes the connector 2i5 to operate to remove ground from conductor 02M to release the selector 266 and remove ground from conductor CI I8 of the line finder 36. Removal of ground from conductor C5 68 causes relay R626 to restore'to return the linefinder circuit 1136 to normal.

As described in the aforementioned patent; the distributor 366 is operative to cause the finder switch of a selected link in the first group of links, such as the finder switch I36 of line 66, to operate and seize a calling line in the second group of lines. The finder switch I36 of the link 66 is operative in a manner substantially identical to that previously explained to find the calling line I6I in the first group of lines when the finder switch I36 is employed to find a calling l0 line such as I66 in the second group of lines. In this case however the switch wipers of the mechanism I 46 encounter battery potential on the control conductor CIO'! of the lower contact set, this battery onthe control conductor CID! being closed over wiper I 46 of the lower wiper set through RAI42 to second test conductor Q326leading to distributor 366. The distributor 366 operates to remove the ground from rotary conductor C324 to thereby release the r0 tary magnet MIII; to close ground to conductor C325 and by way of RAIGO to switching relay RI50. Relay RI56 operates; opens a point in the circuit to the release magnet MIII' at RAI58"; opens a point in the circuit to the rotary magnet MI! I at RAI5I, closes ground byway of switch springs I 86 and I81; RAI56,'and switch springs I and I84 to guard conductor C322 to cause the release of the distributor 366 as previou'sly described, opens a point in the circuit to switching relay I66 at RAI55, and closes a holdf ing circuit to itself from ground on the conductor CH6 through RAI54; Relay RI56 also closes the conductor set I35 extending to the lower wiper set of the switchme'chanism I46 to the trunk line I'I5.j More specifically, the conductors CI3'6; CI'31 andjCI38 of conductor set I35 are respec tively connected, at RAI 5|, RAI52 and RAI53, to the conductors CI !6, CI I! and CI I8 respectively of the trunk line H5. It' is noted that the upper winding of relay R666 is not included in this circuit between trunk lines I35 and H5 and a1 tho the lower windingoi relaylR666 is energized by round at" Ral ltjanq RAI 46, relay R666 never oprates'and therefor the connections established through the linefinder from subscribers substa tions' in the s'econdhl ndreds groupof lines are never subjected to conversation timing andautomatic disconnect. w The finder and associated equipment is released only when the parties hang up as described in the above named patent. Thus it is apparent that calls made from subscribers lines in one hundreds group of lines to other subscribers lines in the same exchange are timed and automatically disconnected during certain timeperiods of the day while similar calls made from subscriberslines in the second hundreds group of lines are not timed and automatically disconnected. I p

I It isv desirable that connection established through' the line finder-switch I36 from subscriber lines in either the first or second hun dredsf group of lines to' a'n' operators position have an unlimited conversation time period, the disconnectionof the switch train being placed under the" control of the called operator. Y This circuit is arranged to prevent the conversation timing equipment from operating on any call to an operatorsposition. On a call from a subscriber linein either group of lines, the linefinder operates to find the calling line and seize the' se-R lector switch as previously described. On calls from lines in the firstgroupof lines, the upper winding of relay R666 will be connected inseries 'with'the line conductor CI I6 while on calls f rom lines in the second group of lines the upper Winding ofrelay R666 willbe omitted from the line' conductor circuit as described. As previously noted, when relay RI60' operates on calls" from lines the first group of lines it closes ground potential on line conductor CIII from the selector switch 266 to one side of the upper winding of relay R666 by way of RAIBZ and the loop in the subscriber station A and battery potential on line conductor CI I6 from the selector switch 200 to the other side of the upper winding of relay R600 by way of RAIGI. As noted, relay R600 will not operate with the potential on its upper winding connected in this manner, the relay being designed to operate only when the potential to its upper winding is reversed. On a call through the selector 200 to operators position 2l0, there is no reversal of battery on the line leads when the operator answers as occurred when the subscriber at station B answered. Since there is no reversal of battery potential on the line conductors, relay R600 never operates and the conversation timing feature is never operative on calls to an operators position.

It is also desirable that manual control of the conversation timing feature be provided to proper parties, at least to the extent that that person may disable the feature during the period that it is normally operative. This to take care of the situation where light traific during the normally heavy traffic period does not warrant the use of conversation timing. A key 242 is provided at a convenient place such as the operators position or exchange attendants desk for disabling conversation timing. Manual operation of the key 242 opens a point in the circuit from the cam springs 21] of timer device 260 to the lower winding of relay R610, thus preventing the operation of relay R610 at any time even though relay R600 may have been operated. Failure of relay R610 to operate renders the conversation timing feature inoperative.

A second method of determining the subscriber lines which are to receive the timing service is by means of finder switch bank levels. As pointed out in the aforementioned patent, the finder switch comprises a switching mechanism of the Strowger type including a bank of fixed contact sets arranged in ten vertical level including upper and lower rows of contact sets, each row of contact sets including ten radically disposed contact sets, each contact set terminating a subscriber line. It is therefore possible, by means of a pair of switch springs fixedly attached to the shaft of the switch mechanism and moveable vertically therewith which maybe arranged to be mechanically operated or to remain unoperated on different ones of the ten levels of the switch bank when the switch carriage" or shaft raises the wipers to those certain bank levels, to discrimiate between different levels of subscribers lines as to the timing service. The following description shows a method whereby the subscriber lines in one or more of the bank levels may have the timing service by arranging that the shaft springs remain unoperated when the switch Wipers reach those particular levels while the subscriber lines on the remaining levels will not have the timing service by providing that the shaft springs operate when the switch wipers reach those levels.

Referring now to Fig. 4, there is shown therein a finder switch 430 similar in many respects to the finder switch I30 described above. Components in Fig. 4 which are similar to components in Fig. l have been numbered so that the tens and units digits are the same as those designating said last components to thereby facilitate an understanding of the operation of Fig. 4.

The finder switch 430 of Fig. 4 differs from the finder switch I30 of Fig. 1 in that the upper winding of the electro-polar relay R100 in Fig. 4 is connected in series with the line conductor C416 of trunk line 415 rather than in series with levels, each line conductor C432 of conductor set 43! so that it may be operated on connections established from either hundreds group of subscriber lines; also the finder switch 430 of Fig. 4 is provided with a well known Strowger normal post switch shaft spring S413 which may be mechanically operated in a well known manner at any desired level of the Strowger switch during vertical stepping of the switch mechanism 440.

The finder switch 430 operates in conjunction with distributor 300, selector circuit 200, and connector circuit 215 to establish a connection between the calling subscriber line l0! in the first group of lines or a, line 106 in the second group of lines and a called subscriber line 230 in a manner similar to that of finder switch I30 in Fig. l with certain modifications. It is noted that the shaft springs S413 of finder switch 430, when closed, shunt the upper winding of electropolar relay R100. The lower winding of relay R is energized when start relay R440 operates on seizure of the finder switch 430 by way of RAMA and RCMS, electro-polar relay R100 not operating on the power of this winding alone. If the call is being made from a subscriber whose line is terminated in a contact set on a bank level of the finder 630 which is to have conversation timing, the shaft springs S413 will not be closed when the wipers of the finder switch 430 are stepped to that level. The upper winding of electro-polar relay R100 will be closed in series with the line conductors of the calling subscriber line in either the first or second hundred groups of lines when switching relays R450 or R460 operate by way of RA45I or RAM respectively and electro-polar relay R100 will operate upon reversal of potential back on the line conductor from the connector 2l5 when the called line answers. The finder switch 430 will then operate in a manner similar to that described previously to time and automatically disconnect the established connection through the linefinder 430.

If the call through finder switch 430 is from a line located on a level of the switch bank of the finder 430 which is not to have conversation timing, the finder switch mechanism is so arranged that the shaft springs S413 will be closed when the switch wipers step to that level and the upper winding of electro-polar relay R100 thereby shunted. Thus when the called subscriber answers the call, the battery reversal on the line conductors in the connector 2I5 will not cause electro-polar relay R100 to operate, the conversation timing equipment thereby remaining disabled.

On calls to an operators position, such as 2l0, reversal of battery never occurs and relay R100 will not operate even on calls from subscriber lines on bank levels having conversation timing, thus calls to an operators position are not timed.

A proper person also has control of the conversation timing feature by means of key 242 as previously explained.

The previous explanation dealt with periodic conversation timing in a linefinder whereby the determination of whether or not a subscriber line with access to the linefinder was to have the conversation timing was made on a group basis, one method being to distinguish between lines depending on the hundreds group in which the line was located and the second method of group discrimination being to distinguish between the lines according to the bank level of the finder switch in which they terminate. It might be thought more desirable to have a system whereby there would be individual discrimination rather than group discrimination, a system whereby the timing and disconnect service could be given to any desired subscriber line in either of the hundreds group of lines and on any level of the switch banks while other subscriber lines in the same hundreds group and on the same switch level would not have the service. Such a third method is disclosed in Fig. taken in conjunction with Figs. 2 and 3, Fig. 5 disclosing a finder circuit 530 similar to the finder circuit I30 of Fig. 1 but having a fourth bank contact and wiper in every set of bank contacts and switch wipers associated with each line having access to the linefinder, linefinder 539 also having additional springs RA559 and RA55il found on the switching relays R550 and R550, respectively. Components in Fig. 5 which are similar to components in Fig. l have been numbered so that the tens and units digits are the same as those designating said last components to thereby facilitate an understanding of the operation of Fig. 5, components having a designation with the hundreds digits of 1 and 6 in Fig. 1 labeled with a designation having the hundreds digits 5 and 8, respectively, in Fig. 5. The subscribers lines which are to have conversation timing have the fourth bank contact, such as 59!, of the set of contacts terminating that particular line strapped together and connected to the timer conductor by way of key 242 and cam springs 21!. Those subscriber lines which are not to have conversation timing have the fourth bank contact associated therewith standing disconnected.

The finder switch 530 operates in a manner similar to that of finder switch I to establish a connection to the called subscriber line 235 through the finder circuit 535 selector 29!], connector 2l5 and line circuit 240. In this case, however, when switching relay R560 operates on calls from subscriber lines in the first hundred group of lines in a manner similar to that described for switching relay Rltt in finder H5, it closes a part of the circuit from the timer conductor 25! to the lower winding of relay Bill, this circuit being traceable from the conductor 25!, through cam springs 25!, key 242, fourth bank contact 59!, wiper 592, RA55B, RABDZ and RA826 and when switching relay R555 operates on calls from subscribers lines in the second hundred group of lines in a manner similar to that described for switching relay Rl5i3 in finder I35, it closes a part of the circuit from the timer conductor 25! to the lower winding of relay BIO by way of cam springs 2M, key 242, fourth bank contact 594, switch wiper 593, RA559, RASBZ and RAMS. Electro-polar relay R895 operates on reversal of battery over the line conductors from the connector 215 when the called subscriber answers as described, closing the circuit previously traced from the timer conductor 25| to the lower winding of relay 8! at RA8Q2, assuming that the call is made during one of the peak load periods of the day. Relay BIO operates and subsequent operations are the same as that described for finder 130 to time and disconnect the connection through the linefinder. It is evident that if the fourth bank contacts 59! or 594 had not been wired as explained but had been left disconnected, operation of relay R850 on reversal of battery potential on the line conductors would not have caused subsequent operation of relay Rim! since the circuit would be open at bank contact 55! or 594. Thus, timing and automatic disconnect would not take place.

It is to be noted that the conversation timing would not be operative on calls to an operator's position and also that the key 242 provides manual control of the conversation timing, for the same reasons as previously explained.

It should be noted that in all three methods explained above, once the conversation timing circuit begins to operate, it cannot be halted except by the voluntary release of the connection by the parties. In other words, operation of the key 242 or cam springs 2M to open the circuit to the lower winding of relay BIB (in Fig. 1) will have no effect after relay 6H! has operated since it looks operated through its upper winding. Relay 600 (Fig. 1) remains operated by means of its lower winding to also prevent a subscriber from causing a break in the conversation timing by a momentary flick of the hookswitch causing a momentary reversal of battery back on the line conductors.

Having described a preferred embodiment of the invention, it is to be understood that various modifications may be made therein, and the appended claims are intended to cover all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a telephone system for establishing connections between calling lines in first and second groups of calling lines and called lines in first and second groups of called lines, circuit means for automatically interrupting an established talking connection, second circuit means for operating said first circuit means only on connec tions established from calling lines in said first group of calling lines to called lines in said first group of called lines, said second circuit means being inoperative to interrupt connections established from calling lines in said first group of calling lines to called lines in said second group of called lines and from calling lines in said second group of calling lines to called lines in said first and second groups of called lines, a clock device controlling said second circuit means, means operated by said clock device during fixed time periods or the day to render said second circuit means operative only during said fixed time periods of the day, a timer device controlling said second circuit means, means operated by said timer device to render said second circuit means operative a certain period of time after the connection is established, and a manual switching means for disabling said first circuit means.

2. In a telephone system, first and second groups of lines, a linefinder circuit having access to said lines, first and second sets of conductors in said linefinder for establishing a connection through said linefinder from lines in said first and second groups of lines, respectively, a control relay connected in only said first set of conductors, means for operating said relay on connections established over only said first trunk line, and circuit discriminating means associated with said relay and rendered operative in' response to the operation of said relay for con-' trolling only the connections extended from calling lines in said first group.

3. In a telephone system, a two hundred point linefinder having access to subscribers line terminal sets divided into two groups of one hundred line sets each, means for completing a talking connection from any one subscriber line terminal set in either of said groups through said line finder, circuit means in said linefinder operative to automatically interrupt the talking connection established therethrough, a second circuit means operative to cause operation of said first circuit means only on connections established from line terminal sets in one of the hundreds groups of line terminal sets, said second circuit means being inoperative to cause interruption of connections established from line terminal sets in the other of said hundreds groups of line terminal sets, a clock device for keeping the time of day, means operated by said clock device during a certain fixed time period of the day, a timer device for measuring a length of time, means operated by said timer device a certain period of time after a connection is established through said linefinder, said second circuit means controlled jointly by said clock operated means and said timer operated means so as to be operated only during said fixed time period and only after the expiration of said certain period of time.

4. In a telephone system as claimed in claim 3, a manual switching means for rendering said second circuit means inoperative.

5. In a telephone system, a two hundred point linefinder having access to subscribers line terminal sets divided into a first and second group of one hundred line terminal sets each, a first and second incoming path in said linefinder, the line terminal sets in said first group of line terminal sets accessible from said linefinder over said first incoming path, the line terminal sets in said second group of line terminal sets accessible from said linefinder over said second incoming path, means for establishing a talking connection through said linefinder from line terminal sets in said first group of line terminal sets over said first incoming path and from line terminal sets in said second group of line terminal sets over said second trunk line, circuit means associated only with said first incoming path operative to automatically interrupt the talking connection established thereover, a timer device for measuring a length of time, means operated by said timer device a certain period of time after a connection is established over said first incoming path, a clock device for keeping the time of day, means operated by said clock device only during certain fixed time periods of the day, said circuit means controlled jointly by said clock operated mean and said timer operated means so as to cause the talking connections established over the first incoming path from line terminal sets in the first group of subscribers line terminal sets to be interrupted only during certain fixed time periods of the day, connections established over said second incoming path remaining uninterrupted at all times.

6. In a telephone system as claimed in claim 5, a key for disabling said timer device to render said circuit means inoperative during said certain fixed time periods.

' 7 In a telephone system, a step-by-step linefinder comprising a ten level contact bank having a plurality of sets of four terminal contacts associated with each level, three contacts of different ones of said sets of contacts being subscriber's line terminals accessible from said linefinder, means for completing a connection from any of said subscriber line terminal sets through said linefinder, a clock device for keeping the time of the day, means operated by said clock device during a certain fixed time period of the day, a timer device for measuring off a length of time, means operated by said timer after a certain period of time, circuit means in said linefinder for automatically interrupting the talking connection 16 established therethrough, a second circuit means including the fourth contact in the set of bank contacts of certain terminal sets for operating said first circuit means to cause interruption only of connections established from said certain line terminal sets, and means controlled jointly by said clock operated means and said timer operated means for causing said second circuit means to be operative only during said fixed time periods of the day and a certain period of time after the connection is established.

8. In a telephone system, as claimed in claim 7, a key circuit for manually disabling said second circuit means.

9. In a telephone system, a linefinder comprising a bank of contacts having a plurality of levels, a plurality of subscribers lines accessible from said linefinder terminating in sets of contacts in each of said levels, means for completing a connection from any of said lines through said linefinder, circuit means operative to automatically interrupt said talking circuit, a timer device for measuring a length of time, means operated by said timer device for rendering said circuit means operative only after a certain period of time has elapsed after the connection was established, a pair of vertical springs in said linefinder, means for operating said springs on connections established over lines terminating in certain levels of said contact bank, a second circuit means including said operated vertical springs for disabling said first circuit means to thereby prevent automatic interruption of connections established from lines in said certain bank levels, lines in the other bank levels having uninterrupted service, a clock device for keeping the time of the day, and means operated by said clock device for controlling said first circuit means to cause it to be operative only during certain times of the day.

10. In a telephone system, a linefinder comprising a ten level bank of contacts, a plurality of sets of contacts in each of said levels, each of said sets being a subscribers line terminal set accessible from said linefinder, means for completing a connection from any of said line terminal sets through said linefinder, a clock device for keeping the time of the day, means operated by said clock device during certain times of the day, a timer device for measuring a length of time, means operated by said timer device after a certain period of time, circuit means in said linefinder responsive to said clock and timer devices for automatically interrupting the talking connection established therethrough a certain period of time after it was established and only during certain times of the day, a pair of vertical springs in said linefinder, means for operating said springs on connections established over line terminal sets in certain levels of said contact bank, and a second circuit means including the operated pair of vertical springs for disabling said first circuit means to thereby prevent interruption of the connection established from line terminal sets in said certain level.

11. In a telephone system as claimed in claim 10, a key for manually disabling said first circuit means.

12. In a telephone system comprising a linefinder switching circuit for use in establishing connections from subscriber lines divided into a plurality of groups of lines, a first wiper set in said linefinder for connection with calling lines in only one of said groups of subscriber lines, a second wiper set in said linefinder for connection with calling lines in another of said groups of subscriber lines only, a first incoming path in said linefinder connected to said first wiper set for use in establishing a connection thereover, a second incoming path in said linefinder connected to said second wiper set for use in establishing a connection thereover, a timer device for measuring off a particular length of time, a control relay connected only in said first incoming path, means for operating said relay only when a connection is extended from a line over said first set of wipers, means for interrupting a connection established through said linefinder, and means controlled by such operation of said control relay for causing said timing device to in turn operate said interrupting means to thereby interrupt only connections established over said first incoming path and only after expiration of a certain period of time.

13. In a telephone system comprising a linefinder switching circuit for use in establishing connections between calling lines divided into a plurality of groups of calling lines and called lines divided into a plurality of groups of called lines, a first wiper set in said linefinder for connection with calling lines in only one of said groups of calling lines, a second wiper set in said linefinder for connection with calling lines in another of said groups of calling lines, a first incoming path in said linefinder connected to said first set of wipers for use in establishing a connection thereover, a second incoming path in said linefinder connected to said second wiper set for use in establishing a connection thereover, an outgoing path in said linefinder common to said incoming paths for use in establishing connections over either of said incoming paths with called lines in either of said groups of called lines, means for interrupting an established connection through said linefinder, an electro-polar relay connected in only said first incoming path, means for operating said electro-polar relay only on calls to a particular one group of called lines over said first incoming path, a timer device for measuring off a particular length of time, a first contact means operated by said timer device a certain length of time after the establishment of a connection and second contact means operated by said electro-polar relay when operated, and circuit means operated jointly by said operated first and second contact means to thereby operate said interrupting means.

14. In a telephone system as claimed in claim 13, a clock device for keeping the time of the day, a third contact means operated by said clock device during certain time periods of the day, said third contact means also controlling said circuit means to cause operation thereof by said first and second contact means only during certain time periods of the day.

CLARENCE E. LOMAX.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,085,624 Allen June 29, 1937 2,333,039 Peterson Oct. 26, 1943 

